We investigated in the influence of regional left ventricular asynchrony on impaired global left ventricular diastolic filling in patients with hypertrophic cardiomyopathy using radionuclide angiography. Previous studies indicate that left ventricular diastolic filling is impaired in hypertrophic cardiomyopathy and is improved during verapamil therapy. We subdivided the left ventricular region of interest on the radionuclide angiogram into 20 sectors and computed the time interval from the R wave to minimum volume of each sector's time activity curves. The inter-sector standard deviation of time minimum volume (SDTMV) was used as an index of relative left ventricular regional asynchrony. This index was increased in hypertrophic cardiomyophathy patients compared to normal, indicating asynchronous regional function. After 1-2 weeks of verapamil, SDTMV significantly decreased, indicated more synchronous LV regional behavior, specifically greater systolic temporal homogeneity. This improvement after verapamil was associated with no change in global LV ejection fraction or peak ejection rate; however, global rapid-diastolic filling improved, manifested by and increased peak filling rate. These data suggest that in many hypertrophic cardiomyopathy patients, impaired global left ventricular filling may be associated, in part, with non-unoformity of systolic function and that verapamil's beneficial effects on left ventricular diastolic function may be mediated by reduction in regional asynchrony.